The present invention concerns a control/fire damper for ducts in ventilation installations, said control/fire damper comprising a shell constituting a flow duct, a closing member disposed inside the flow duct and which in fire damper use continuously tends to close under spring action, said control/fire damper being provided with a clamping counterpart attached to the closing member and with a clamping device passing through the shell and arranged to fix the counterpart by friction clamping in desired position, and said clamping device being clampable and releasable from outside the shell.
At present, in a number of structural designs known in the art, fixing of the closing plate in desired position is effected outside the damper by the aid of screw clamping between a sector plate or equivalent and its counterpiece. However, structures of this kind have the drawback of a certain space requirement outside the duct, which frequently entails difficulties in installation. In addition, the construction is susceptible to damage; it interferes with the lagging of the duct; and its appearance is not always acceptable, as is stated e.g. in the Norwegian patent application No. 802081.
In another structure known in the art, the fire limiter of the Finnish Pat. No. 54767, the fuse is a separate fuse attached to an adjusting cable or wire passing through the shell, and the closing plate is turnable into desired position with reference to the flow duct by the aid of the adjusting cable or wire, in order to produce the desired throttling. A drawback of this design is, in addition to inconvenient restoring operation after the closing plate has been trigged, that the fuse replacement operation is exceedingly cumbersome, and it is difficult after such replacement to reposition the closing plate exactly as before if the new fuse has different dimensions.